A syringe is an indispensable apparatus to medical treatment. All current syringes are designed as being disposal so as to prevent cross infection. However, such disposal syringes can be reused if they are not destroyed artificially. In order to prevent the current disposal syringes from being reused, which may result in cross infection and disease spread, many types of syringes have been invented. For example, in a syringe where the needle retracts into the barrel when the push rod is drawn back, the needle may come out again when a force is applied, which may still result in cross infection. In another needle-retractable safety syringe disclosed in the patent No. 200410017938.0, the needle will retract into the barrel when the push rod is drawn back, with the needle tip tilting aside and difficult to be drawn out. However, it is easy for the sharp needle tip to pierce through the barrel wall, which is soft and generally made of common polypropylene (PP). Therefore, this syringe may still result in cross infection. The following three methods may be adopted for the sake of safety: 1. Increasing the thickness of the barrel wall; 2. adding a stiffening agent into the polypropylene raw material; and 3. choosing a barrel with low rigidity. However, the cost will thus be increased, and the sharpness of the needle tip lowered, which may bring much suffering to the patients. The push rod can also be provided with a defective portion. The syringe can be destroyed after injection by breakage of the push rod. However, such a syringe can still be reused so long as the broken push rod is replaced with a new one. Therefore, the complete safety cannot be guaranteed.
Contents of the Invention
A purpose of the present invention is to provide a self-destroying syringe, whose push rod can be locked after injection so that it cannot be reused or replaced.
In order to achieve the above purpose, a technical solution of the present invention is as below:
A new self-locking self-destroying safety syringe is provided, comprising a hollow barrel, a push rod sliding within the barrel, a rubber plug in front of the push rod, and a needle seat in front of the barrel. It has the following features: The push rod is provided with a round platform, which is provided with an elastic ratchet that slantingly extends toward the inner wall of the barrel; the barrel is provided at the end with an increasing-diameter portion; at the transient position between the normal-diameter portion and the increasing-diameter portion of the barrel is located a slanting step, below which is a groove where the elastic ratchet can be catched when the push rod is drawn backward; and the increasing-diameter portion is provided inside with a circlip that can press against the bottom of the round platform.
The circlip, dynamically fitted with the inner wall of the increasing-diameter portion at the end of the barrel, can move forward and backward axially without moving out of the barrel, with the moving distance longer than the distance from the tip of the elastic ratchet on the push rod to the bottom of the round platform; the internal diameter of the upper end of the circlip is slightly smaller than that of the barrel at the slanting step; the circlip is provided at the inner circle with a slope; when the push rod is installed, the elastic ratchet can move forward and furl inward along the slope, and the round platform can stretch the inner bore of the circlip larger and get into it.
The increasing-diameter portion at the end of the barrel is provided on the inner wall with a circle of big groove that is dynamically fitted with the circlip; the big groove can butt at its upper end against the top end of the circlip, and is provided at the lower end with a flanged step; the circlip is provided at the upper outer circle with a flange; and the flanged step butts against the bottom end plane of the outer circle flange.
The external diameter of the round platform on the push rod is smaller than or equal to the minimal internal diameter of the barrel at the slanting step, but bigger than the minimal internal diameter of the circlip.
There are at least two elastic ratchets that are symmetrically positioned; the distance between the symmetrical ratchet tips is smaller than the internal diameter of the normal-diameter portion of the barrel, but bigger than the minimal internal diameter of the barrel at the slanting step.
The tip of the elastic ratchet extends slantingly up to the front end of the barrel.
There are four elastic ratchets that are symmetrically positioned.
The groove is a circle of clamping groove, whose upper end plane is a slope or a plane that extends outward along the direction of the tip of the elastic ratchet; and the diameter of the groove at the side wall is bigger than the distance between the two symmetrically-positioned ratchet tips.
For a syringe with the above-mentioned structure, the push rod can be locked after injection in the following way: The barrel is provided at the end with the increasing-diameter portion; the self-locking mechanism can be located at the rear end of the barrel; the push rod is provided with the elastic ratchet that extends to the inner wall of the barrel; the elastic ratchet gets stuck into the groove when the push rod is drawn backward; the slanting step above the elastic ratchet prevents the push rod from moving forward, while the circlip below the elastic ratchet presses against the bottom of the round platform of the push rod so as to prevent the push rod from moving backward; and under the action of the groove, the elastic ratchet cannot move radially either.